Calculus works by making visible the infinitesimally small.

I've never met Hans Rosling, but I just knew him through his many YouTube videos, and they were absolute dynamite.

Hans Rosling typically would go into the room, and he would ask the audience questions. Often they had to answer them with clickers or raising their hands or something. We get [data] wrong because 50 years ago that wasn't the case and because we haven't had these graphics we don't realize that over the last 30, 40, 50 years things have changed dramatically. And you see how the world has been getting a better, safer, more homogeneous place. It just has.

Calculus works by making visible the infinitesimally small.

The whole apparatus of the calculus takes on an entirely different form when developed for the complex numbers.

A PhD in Mathematics is three years of guessing it wrong, plus one week of getting it right and writing a dissertation.

I certainly do care about measuring educational results. But what is an 'educational result?' The twinkling eyes of my students, together with their heartfelt and beautifully expressed mathematical arguments are all the results I need.